Laser diodes are operated at high injected current densities, which create high-energy electrons and holes, thermal gradients, potential for strain fields, and a high nonradiative recombination rate inside the active region. Thus the P-N junction and optical elements of a laser diode can react very quickly to changes in voltage or current. Therefore, in order to be effective, an ESD protection device and method should preferably be implemented as a proactive measure, by preventing the over-voltage or over-current. Among the limitations known from semiconductor lasers, catastrophic optical damage (COD) is perhaps the most spectacular power-limiting mechanism. It occurs when the semiconductor junction is overloaded by exceeding its power density and absorbs too much of the produced light energy, leading to melting and. Table 1 summarizes common failure modes and mechanisms of LEDs and laser diode devices. LEDs have two primary failure modes described in a and b.
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